A graffiti artist painting the steel shutter of a hairdresser's shop in Barcelona. Photograph: Cesar Casellas

Barcelona shopkeepers believed they were beautifying their city when they commissioned graffiti artists to paint the shutters protecting their shopfronts rather than leaving them to be defaced by vandals. Now they face being fined up to €600 (£510) by city authorities intent on cracking down on "antisocial behaviour".

The council says the artists' graffiti "degrades the urban fabric" as much as washing hung from balconies, and have fined more than 160 businesses this year.

"The law regards graffiti as something that soils the public space, devalues our heritage and visually degrades the urban fabric," a city spokesman said.

The groups behind the schemes to paint over the steel security barriers say they are oversubscribed from businesses who want to prevent the scribbled spray-painted signatures, or "tags", that are epidemic in the city. Taggers respect the art and do not paint over it.

Persianas Lliures (Free Roller Blinds), says it has 250 orders outstanding, and Enrotlla't – a play on "roll up" and "have fun" – says it is struggling to keep up with demand. In one weekend, Enrotlla't painted 47 blinds in the Gràcia district.

Jordi Llobell, the group's founder, said its mission was to encourage the best art. "The shopkeepers can visit our website and see the work of the various artists and choose the one that is most to their taste," he added.

Llobell blames the plague of tagging on the crackdown on graffiti that began 10 years ago. Rather than be caught painting a mural, grafiteros opted for a quick scribble and run. "There will always be something anarchic about graffiti because it is essentially about freedom," he said. "But unless you want to get caught, you will paint in places where it's legal to do so.

"It's a big contradiction that they won't let us paint in public spaces, even with the owners' permission, when the same council mounts expensive exhibitions about graffiti in art galleries."

Although Barcelona likes to present itself as an relaxed, liberal city, authorities have begun cracking down on "antisocial" behaviour in recent years.

Lying on park benches, locking your bike to a lamppost and drinking alcohol in public are all on a growing list of offences punishable with large fines.

The grafiteros point to the more liberal attitude that cities such as Madrid and Valencia take towards their work. A magazine recently invited 100 grafiteros to paint 100 shops in Madrid's Malasaña district in a single night.

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